Persistence of botulinum toxin in patients' serum: Alaska, 1959-2007.

Persistence of circulating toxin in patients with foodborne botulism is not well characterized. Recommendations for administration of botulinum antitoxin are ambiguous for patients with late-presenting disease, such as a Florida woman with toxin-positive serum 12 days after toxin ingestion. We reviewed Alaska records of foodborne outbreaks of botulism that occurred during 1959-2007 to examine the period after ingestion during which toxin was detected. Of 64 cases with toxin-positive serum, toxin was detected up to 11 days after ingestion. The findings from Alaska and Florida support administration of antitoxin up to 12 days after toxin ingestion but do not indicate when circulating toxin should no longer be present.